Tenuifolin Attenuates Amyloid-β42-Induced Neuroinflammation in Microglia Through the NF-κB Signaling Pathway

Background: Inflammation and oxidative stress are believed to play an important role in the pathogenesis of Alzheimer's disease (AD). Tenuifolin (TEN) is a natural neuroprotective compound extracted from Polygala tenuifolia Willd, which may improve cognitive symptoms. Objective: This study was designed to evaluate the protective effect of TEN on inflammatory and oxidative stress induced by amyloid-beta (A beta)(42) oligomers in BV2 cells, and to explore the underlying mechanisms. Methods: We conducted cell viability assays to estimate drug toxicity and drug effects on cells. Quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assays were performed to detect the release of inflammatory factors. Nitric oxide (NO) assays were used to measure the degree of oxidative stress. Western blot and immunofluorescence analysis were used to explore the influence of TEN on the nuclear factor-kappa B (NF-kappa B) pathway. Results: Pretreatment of BV2 microglial cells with TEN inhibited the release of tumor necrosis factor-alpha, interleukin-6, and interleukin-1 beta, alleviated NO-induced oxidative stress by inhibiting the expression of inducible nitric oxide synthase and cyclo-oxygenase-2, and protected SH-SY5Y cells from the toxicity induced by the medium conditioned by BV2 cells previously exposed to A beta(42) oligomers. Moreover, TEN suppressed upstream activators of NF-kappa B, as well as NF-kappa B translocation to the nucleus in BV2 microglial cells. Conclusion: This study demonstrates that TEN can protect SH-SY5Y cells from A beta(42) oligomer-induced microglia-mediated inflammation, and oxidative stress by downregulating the NF-kappa B signaling pathway.